The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some of such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Metal or steel surfaces are in many applications marked or coloured with various marks or colours. The purpose may be esthetical or sometimes the purpose is to protect the surface. A common method for colouring metal surfaces is to use paints, adhesive labels, etching or electrolytic colouring. These methods are very limited and the processes are not flexible. This applies especially applications where different markings are required on the metal surfaces. The markings and colours are not durable. In addition, the methods may involve the use of paints and solvents which are harmful to environment.
Marking small steel surfaces with a laser beam has been known for a few years in laboratory environments. However, practical applications of the known techniques have not been proposed and the obtained markings are simple.